Play as Inferno.

I know one tactic on how a demon with such stats can easily defend in a castle. It’s simple: take Imps and divide them into a couple of stacks. Then take Cave Lords and also divide them into 2 stacks. You get a deadly machine for throwing fireballs, and if the Imps are also upgraded, the Orc will definitely be in trouble; only horns and legs will remain of him. One player used this tactic against me when I was trying to besiege a demon castle with Necropolis units, and he regretted it.